Over the last 2 1/2 years we have been involved in behavioral treatment of young autistic children (children less than 46 months of age if echolalic, and 40 months of age if mute). We have randomly assigned such children to 2 groups: Treatment I whih receives more than 20 hours of treatment per week, and Treatment II, which receives less than 10 hours per week. Pretreatment assessment includes a psychiatric/neurological evaluation, behavioral recordings of free-play and social behavior, psychological testing (the Bayley and Vineland), autism diagnostic checklist, etc. Treatment is modeled on a behavior modification framework, with emphasis on training the parent as the child's therapist. Post-treatment measures include the child's ability to function independently in, and adequately adjust to, and learn from, normal school placement. To date we have completed treatment of 11 children in Treatment I, and 9 children in Treatment II. Preliminary data suggests a recovery rate of 54 to 64 percent in Treatment I, and 0 to 11 percent in Treatment II. These are very encouraging data, considering the poor prognosis of autistic children. Because of the large amount of treatment time we have had to invest in these children, we have been able to see a relatively small number. Considering our lack of information about young autistic children (their base-rate recovery rate is unknown), the main weakness in the present study centers on the small N per group. It is with the hope of increasing our sample size (to 20 children per group) that we apply for supplemental funds for the remaining 3 years of the grant (up to September, 1979).